Elbow prosthesis

ABSTRACT

A prosthetic joint kit, particularly well suited for an elbow, transmits load through the prosthetic joint through a pair of spherically shaped bearing surfaces so as to transmit load over a relatively large area rather than at a point or over a line of contact. The prosthetic joint kit may be configured in a modular manner wherein a plurality of interchangeable stem structures, bearing structures and/or bearing inserts of various types are available. Construction in this manner enables a surgeon to configure the prosthetic joint to best suit the needs of the patient. For example, the surgeon may employ a modular flange for compressing a bone graft, a tissue fastener for securing soft tissue to a portion of the prosthetic joint, a cam for limiting the amount by which the prosthetic joint articulates or a bearing insert for tailoring the degree of varus/valgus constraint.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/333,140 filed on Jan. 15, 2003, now U.S. Pat. No. 7,247,170, which isa National Stage of International Application No. PCT/US01/22338, filedJul. 17, 2001, which claims the benefit of U.S. Provisional ApplicationNo. 60/219,103, filed on Jul. 18, 2000. The disclosure(s) of the aboveapplication(s) is (are) incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to prosthetic devices used inelbow arthroplasty and more particularly to a modular elbow prosthesis.

BACKGROUND OF THE INVENTION Background Art

Linked or constrained elbow prostheses are known which comprise simplehinge arrangements, one component of which is attached to the end of thehumerus and the other component of which is attached to the end of theulna. The humeral component includes a shaft that is cemented into aprepared cavity in the end of the humerus, and the ulnar componentincludes a shaft, that is cemented to the end of the ulna. Thecomponents of the prothesis are connected together by means of a hingepin so that the prothesis allows a single degree of freedom of movementof the ulna relative to the humerus.

One example of a linked elbow prostheses is disclosed in U.S. Pat. No.6,027,534 to Wack et al. In several respects, the linked embodiment ofthe '534 patent is typical of the designs for linked elbow prostheses inthat it includes a humeral stem that terminates at a yoke at its distalend, a bearing component, a retaining pin and an ulna stem. The bearingcomponent includes an oversized hole that is aligned with thelongitudinal axis of the bearing and adapted to accept the retaining pinin a slip-fit condition. The distal end of the bearing component iscoupled to the ulna stem. Despite the relatively widespread use ofdesigns of this type, several drawbacks have been noted.

One significant drawback concerns the assembly of the elbow prosthesisafter the surgeon has cemented the humeral and ulna stems to theirrespective bones. In using such conventionally configured linked elbowprosthesis devices, it is frequently necessary for the surgeon to drilla fairly large hole through the humerus to that the retaining pin may beinserted to the yoke of the humeral stem and the humeral bearingcomponent. As a high degree of accuracy is typically required to ensureproper alignment between the hole in the humerus and the hole in theyoke of the humeral stem, a significant cost can be associated with thisstep in the installation of an elbow prosthesis due to the cost of thetooling used and the amount of time required to complete this step. Theother method for attaching the prosthetic device includes inserting thedevice in its linked condition or placing the remaining piece into theyoke prior to fully seating the humeral component into the bone. Thislater method is typically somewhat difficult, given the limited amountof joint space that is available and the time constraints associatedwith the use of a PMMA bone cement.

Unlinked, or unconstrained, elbow prostheses are known which are similarto linked elbow prostheses but do not have a specific component whichmechanically couples the humeral and ulnar stems together. Rather, theprosthetic device is held together by the patient's natural softtissues. One example of an unlinked elbow prostheses is also disclosedin U.S. Pat. No. 6,027,534 to Wack et al. In several respects, theunlinked embodiment of the '534 patent is similar to the linkedembodiment discussed above in that it includes a humeral stem thatterminates at a yoke at its distal end, a humeral bearing component, aretaining pin, an ulnar bearing component and a ulnar stem. The outersurface of the humeral bearing is contoured to match the contour of theulnar bearing component. Despite the relatively widespread use ofdesigns of this type, several drawbacks have been noted.

For instance, a retaining pin that is transverse to the longitudinalaxis of the patient is employed, thereby making its removal difficult ifa bearing need to be replaced.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a prostheticjoint kit which transmits load through mating bearing components over aspherically shaped area so as to minimize stresses in the bearingcomponents, more accurately mimic normal joint motion and provide forease of assembly and revision.

In one preferred form, the present invention provides a prosthetic jointkit having a first bearing component and a second bearing component. Thefirst bearing component includes a pair of condyle portions, each ofwhich having a spherically shaped bearing portion. The second bearingcomponent includes a pair of spherical bearing portions which areconfigured to engage the spherically shaped bearing portions of thefirst bearing component.

It is another general object of the present invention to provide aprosthetic joint kit having a high degree of modularity to permit asurgeon to easily configure the prosthetic joint kit to a patient.

In another preferred form the present invention provides a prostheticjoint kit having a plurality of modular and interchangeable jointcomponents which permit a surgeon to easily configure the prostheticjoint kit to a patient. Modularity is achieve through a plurality ofinterchangeable components such as stem structures, bearing componentsand bearing inserts.

It is yet another general object of the present invention to provide aprosthetic joint kit having a plurality of interchangeable bearinginserts which permit a surgeon to tailor the degree of varus/valgusconstraint in a desired manner.

In another preferred form, the present invention provides a prostheticjoint kit having a plurality of interchangeable bearing inserts, each ofwhich having a pair of spherical depressions. Each of the spericaldepressions has a first portion and a second portion, with the secondportion being formed in a manner that defines the degree of varus/valgusconstraint. It is a further object of the present invention to provide aprosthetic joint kit which effectively limits the amount by which theprosthetic joint will articulate.

In yet another preferred form, the present invention provides aprosthetic joint kit having a cam structure which is coupled to a firststem structure such that the first stem structure contacts a second stemwhen the first stem structure has been rotated to a predeterminedposition relative to the second stem structure.

It is yet another object of the present invention to provide aprosthetic joint kit which employs a spherically-shaped bearing surfaceto transmit load between stem structures yet does not require fastenersor other hardware to link the stem structures together.

In another preferred form, the present invention provides a prostheticjoint kit having a first stem structure with a retaining structure and afirst spherical bearing surface and a second stem structure with aretaining aperture and a second spherical bearing surface. The retainingaperture is configured to receive the retaining structure when the firststem structure is at a first orientation relative to the second stemstructure. Relative rotation of the first stem structure from the firstorientation causes retaining structure to engage a portion of theretaining aperture which precludes the withdrawal of the retainingstructure therefrom. The retaining aperture and retaining structure aresized so as not to transmit load therebetween, thereby ensuring thatload is transmitted between the spherical bearing surfaces of the firstand second stem structures.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and features of the present invention will becomeapparent from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is an exploded perspective view of a linked prosthetic joint kitconstructed in accordance with the teachings of a first aspect of thepresent invention;

FIG. 1A is an exploded perspective view of a linked prosthetic joint kitsimilar to that of FIG. 1 but constructed in accordance with a firstalternate embodiment of the first aspect of the present invention;

FIG. 2 is a longitudinal cross-sectional view of the linked prostheticjoint kit of FIG. 1 implanted in the arm of a person;

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is a exploded perspective view of an unlinked prosthetic jointkit constructed in accordance with the teachings of a first aspect ofthe present invention;

FIG. 5 is a longitudinal cross-sectional view of the unlinked prostheticjoint kit of FIG. 4 implanted in the arm of a person;

FIG. 6 is an exploded plan view of a linked prosthetic joint kitconstructed in accordance with a second alternate embodiment of thefirst aspect of the present invention;

FIG. 7 is an enlarged portion of the linked prosthetic joint kit of FIG.6;

FIG. 8 is an exploded plan view of a linked prosthetic joint kitconstructed in accordance with a third alternate embodiment of the firstaspect of the present invention;

FIG. 9 is a exploded side elevation view of a portion of a joint kitconstructed in accordance with the teachings of a second aspect of thepresent invention;

FIG. 10 is an exploded side elevation view of a portion of a joint kitconstructed in accordance with a first alternate embodiment of thesecond aspect of the present invention;

FIG. 11 is an exploded side elevation view of a portion of a joint kitconstructed in accordance with a fourth alternate embodiment of thesecond aspect of the present invention;

FIG. 12 is a longitudinal cross-sectional view of a portion of a jointkit constructed in accordance with a fourth alternate embodiment of thesecond aspect of the present invention;

FIG. 13 is an exploded side elevation view of a portion of a joint kitconstructed in accordance with a fifth alternate embodiment of thesecond aspect of the present invention;

FIG. 14 is a cross-sectional view taken along the line 14-14 of FIG. 13;

FIG. 15 is a cross-sectional view of a portion of a joint kitconstructed in accordance with a sixth alternate embodiment of thesecond aspect of the present invention;

FIG. 16 is an exploded side elevation view of a portion of linkedprosthetic joint kit constructed in accordance with the teachings of apreferred embodiment of a third aspect of the present invention;

FIG. 17 is a cross-sectional view taken along the line 17-17 of FIG. 16;

FIG. 18 is a cross-sectional view taken along the line 18-18 of FIG. 16;

FIGS. 19A through 19D are side elevation views of bearing insertsconstructed with varying degrees of varus/valgus constraint;

FIG. 20A is an exploded side elevation view of a portion of a linkedprosthetic joint kit constructed in accordance with the teachings of afirst alternate embodiment of the third aspect of the present invention;

FIG. 20B is an exploded side elevation view of a portion of a linkedprosthetic joint constructed in accordance with the teachings of secondalternate embodiment of the third aspect of the present invention;

FIG. 20C is a side view of an alternately constructed pin for linkingthe bearing structures of the second alternate embodiment of the thirdaspect of the present invention;

FIG. 21 is a bottom plan view of a portion of the linked prostheticjoint kit of FIG. 20 illustrating the bearing insert in greater detail;

FIG. 22 is a side elevation view of a portion of the linked prostheticjoint kit of FIG. 20 illustrating the clip member in greater detail;

FIG. 23 is a longitudinal cross-sectional view of a linked prostheticjoint kit constructed in accordance with the teachings of a preferredembodiment of a fourth aspect of the present invention;

FIG. 24 is a top plan view of the linked prosthetic joint kit of FIG.23;

FIG. 25 is an exploded top plan view of a linked prosthetic joint kitconstructed in accordance with the teachings of a preferred embodimentof a fifth aspect of the present invention;

FIG. 26 is a longitudinal cross-sectional view of the linked prostheticjoint kit of FIG. 25;

FIG. 26 a is a longitudinal cross-sectional view of the linkedprosthetic joint kit according to various embodiments;

FIG. 27 is a longitudinal cross-sectional view similar to that of FIG.2, but illustrating the stem with an integrally-formed flange forcompressing a bone graft;

FIG. 28 is a side view illustrating a stem with an integrally-formed,resilient flange for compressing a bone graft;

FIG. 29 is a longitudinal cross-sectional view similar to that of FIG.2, but illustrating the stem of FIG. 28;

FIG. 30 is a longitudinal cross-sectional view similar to that of FIG.29, but illustrating the resilient flange as being fixedly but removablycoupled to the stem;

FIG. 31 is a partially broken-away exploded perspective viewillustrating an alternative coupling means for coupling the modularflange to the stem;

FIG. 32 is a longitudinal cross-sectional view similar to that of FIG.2, but illustrating the alternative coupling means of FIG. 31;

FIG. 33 is a view similar to that of FIG. 31 but illustrating a secondalternative coupling means;

FIG. 34 is a view similar to that of FIG. 31 but illustrating a thirdalternative coupling means;

FIG. 35 is a longitudinal cross-sectional view similar to that of FIG.2, but illustrating the alternative coupling means of FIG. 34.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1, 2 and 3 of the drawings, a linked prostheticjoint device constructed in accordance with the teachings of a firstaspect of the present invention is generally indicated by referencenumber 10. Although the particular prosthesis illustrated an discussedrelates to a prosthesis for use in reconstructing an elbow, it will beunderstood that the teachings of the present invention haveapplicability to other types of linked and unlinked prosthetic devices.As such, the scope of the present invention will not be limited toapplications involving elbow prosthesis but will extend to otherprosthetic applications.

In the particular embodiment illustrated, linked prosthetic joint 10 isshown to include a first stem structure 12, a second stem structure 14,a first bearing component 16, a second bearing component 18, a modularflange 20 and a tissue fastener 22. First stem structure 12 includes aproximal portion 30 and a distal portion 32. Proximal portion 30includes a stem member 34 which is adapted to fit within the medullaryanal 36 of a humerus 38. Distal portion 32 includes a generally U-shapedmember 40 which is fixedly coupled to the distal end of proximal portion30. U-shaped portion 40 includes a pair of spaced-apart legs orfurcations 42. A threaded fastener aperture 44 extends perpendicularlythrough each of the furcations 42.

Second stem structure 14 includes a distal portion 50 which is adaptedto fit within the medullary canal 52 of an ulna 54. Second stemstructure 14 also includes a proximal portion 56 which is coupled tosecond bearing component 18. In the particular embodiment illustrated,second bearing component 18 is fixedly coupled to second stem structure14. However, second bearing component 18 may also be releasably coupledto second stem structure 14 as shown in FIGS. 9 through 12.

First bearing component 16 includes a pair of condyle portions 60, a pinportion 62 and a pair of fasteners 64. Condyle portions 60 and pinportion 62 are formed from a suitable material, such as cobalt chromiumalloy. Each condyle portion 60 is shown to include a spherically-shapedbearing portion 66, slotted aperture 68, a pin aperture 70 and amounting aperture 72. The pair of spherically shaped bearing portions 66collectively form a first bearing surface. Pin aperture 70 is sized toreceive an end of pin portion 62 to permit pin portion 62 to slidinglyengage condyle portions 60. Pin 62 can also be fixedly coupled with oneof said condyle portion 60 and slidingly engage second of said condyleportion 60. Each of the slotted apertures 68 is sized to slidinglyengage one of the furcations 42.

Second bearing component 18 is shown to include a cage portion 80 whichis fixedly coupled to the proximal portion 56 of second stem structure14 and a bearing member 82 which is fixedly coupled to the cage portion80. Bearing member 82 includes a pair of spherical bearing portions 84which are configured to engage the spherically shaped bearing portions66 of the condyle portions 60. The pair of spherical bearing surfaces 84collectively form a second bearing surface that mates with the firstbearing surface. Bearing member 82 also includes a through hole 86 whichis adapted to receive pin portion 62, preferably without transmittingload therebetween (i.e., pin portion 62 preferably does not contact thesurfaces of through hole 86). In the particular embodiment illustrated,bearing member 82 is fabricated from polyethylene which as been moldedto cage portion 80. Alternatively, bearing member 82 may be fabricatedfrom any other appropriate material such as a stainless steel, ceramic,pyrolytic carbon, cobolt chrome (CoCr) etc.

To use linked prosthetic joint 10, first stem structure 12 is implantedin humerus 38 such that proximal portion 34 is located in the medullarycanal 36 of the humerus 38 as shown in FIG. 2. Second stem structure 14is similarly implanted in ulna 54 such that distal portion 50 is locatedin the medullary canal 52. Pin portion 62 is next inserted to the pinaperture 70 of one of the condyle portions 60 and the opposite end ofpin portion 62 is placed through hole 86 and into the pin aperture 70 ofthe other one of the condyle portions 60. Second bearing component 18 ispositioned adjacent the distal portion 32 of first stem structure 12,furcations 42 are aligned to their respective slotted aperture 68 andcondyle portions 60 are slidingly engaged to furcations 42. Fasteners 64are inserted through their respective mounting apertures 72 andthreadably engaged to their threaded fastener aperture 44. When fullyseated, each of the fasteners 72, extends through its respectivefurcation 42 to prevent condyle portion 60 from rotating relative to thefurcation 42. At this point, first and second bearing components 16 and18 hingedly couple first and second stem structures 12 and 14 togetherin a linked or constrained manner.

Construction of linked prosthetic joint 10 in this manner is highlyadvantageous in that is permits the surgeon to insert the first andsecond stems structures 12 and 14 prior to or after assembling linkedprosthetic joint 10, as well as permits linked prosthetic joint 10 to beassembled in a relatively small space as compared to most of the otherprosthetic joins that are known in the art. Furthermore, the sphericalconfiguration of first and second bearing surfaces 66 and 84 permits theload which is transmitted through linked prosthetic joint 10 to bespread out over a relatively large area, rather than concentrated at asingle point or over a line of contract to thereby improve thedurability of linked prosthetic joint 10.

Modular flange 20 may be employed to increase the resistance of firststem structure 12 to rotation within medullary canal 36. In FIGS. 1 and2, modular flange 20 s is shown to include an internally treadedfastener 90, and a unitarily formed flange structure 92 having a mountmember 94 and a flange member 96. Mount member 94 includes a locatingcylinder 94 a which is fixedly couple to flange member 96 at its baseand an externally threaded fastener 94 b which is coupled to an oppositeside of locating cylinder 94 a. A mounting hole 98, which is sized toreceive fastener 94 b, extends through internally threaded fastener 90.A bore 100 formed through the base 102 of U-shaped portion 40 has afirst portion 104 which is tapered at one end to engage the edges ofinternally threaded fastener 90 and second portion 106 which is counterbored at the other end to engage the locating cylinder 94 a of mountmember 94. Internally threaded fastener 90 is threadably engaged tofastener 94 b to fixedly but removably couple modular flange 20 to firststem structure 12.

Modular flange 20 may be employed to generate a clamping force whichclamps a portion 108 of the humerus 38 between the proximal portion 34of the first stem structure 12 and the flange member 96. Preferably, abone graft 110 is employed in conjunction with modular flange 20 suchthat the clamping force produced by modular flange 20 is alsotransmitted to bone graft 110 to promote the attachment of bone graft110 to humerus 38 and the subsequent growth of bone graft 110. Thoseskilled in the art will understand that alternatively, a flange (notshown) which is unitarily formed with first stem structure 12 may beincorporated into linked prosthetic joint 10 to thereby increase theresistance of first stem structure 12 to rotation within medullary canal36. However, a flange which is unitarily formed with first stemstructure 12 could not be employed to generate a clamping force whichclamps a portion 108 of the humerus 38 between the proximal portion 34of the first stems structure 12 and the flange.

Tissue fastener 22 is shown in FIGS. 1 and 2 to be a device forattaching soft tissue, such as tendons 130, to linked prosthetic joint10. In this regard, the specific configuration of tissue fastener isbeyond the scope of this disclosure. Example of suitable tissuefasteners are discussed in U.S. Pat Nos. 5,380,334, 5,584,835, 5,725,54,5,840,078 and 5,980,557 which are hereby incorporated by reference as iffully set forth herein.

In the particular embodiment illustrated, tissue fastener 22 is shown toinclude a tissue clamp 132 and a threaded fastener 134. Tissue clamp 132includes an annular base 136 and a pair of prongs 138. Prongs 138 areforced through the soft tissue (e.g. tendons 130). Threaded fastener 134is inserted through a hole in base 136 and threadably engaged to secondstem structure 14 to fixedly but releasably couple tissue fastener 22and the soft tissue to second stem structure 14. Those skilled in theart will understand that tissue fastener 22 may also be used inconjunction with first stem structure 12.

In FIG. 1A, a linked prosthetic joint device constructed in accordancewith the teachings of an alternate embodiment of the first aspect of thepresent invention is generally indicated by reference numeral 10 a.Linked prosthetic joint 10 a is shown to include first stem structure12, second stem structure 14, first bearing component 16 a, secondbearing component 18 a, modular flange 20 and tissue fastener 22.

First bearing component 16 a is similar to first bearing component 16 inall respects except that it is unitarily formed. Accordingly, pinportion 62 a is not removable form condyle portions 60 a. Second bearingcomponent 18 a is similar to second bearing component 18 in all respectsexcept that an insertion aperture 150 extends form through hole 86 aoutwardly through bearing member 82 a and cage portion 80 a.Accordingly, insertion aperture 150 renders the area of second bearingsurface 84 a somewhat smaller than second bearing surface 84. Secondbearing surface 84 a is otherwise identical to second bearing surface84.

To use linked prosthetic joint device 10 a, first and second stemstructures 12 and 14 are initially inserted to the humerus and ulna andfirst bearing component 16 a is fastened to the first stem structure 12using techniques similar to that discussed above for prosthetic jointdevice 10. First bearing component 16 a is fastened to the first stemstructure 12 using techniques similar to that discussed above forprosthetic joint device 10. First bearing component 16 a is thenpositioned adjacent second bearing component 18 a such that pin portion62 a is in insertion aperture 150. Pin portion 62 a is then forcedtoward through hole 86 a. The distal end 152 of insertion aperture 150is smaller than pin portion 62 a to permit bearing member 82 a to engagepin portion 62 a in a snap fit manner, so as to inhibit theunintentional withdrawal of pin portion 62 a from through hole 86 a. Asdiscussed above, through hole 86 a is preferably larger in diameter thanpin portion 62 a. At this point, first and second bearing components 16a and 18 a hingedly couple first and second stem structures 12 and 14together in a linked manner.

In FIGS. 4 and 5, an unconstrained or unlinked prosthetic joint deviceconstructed according to a first aspect of the present invention isgenerally indicated by reference number 10′. Unlinked prosthetic joint10′ is shown to include a first stem structure 12, a second stemstructure 14, a first bearing component 16′, a second bearing component18′, a modular flange 20 and a tissue fastener 22. Unlinked prostheticjoint 10′ is shown to be operatively associated with a humerus 38′ andan ulna 54′ (FIG. 5), but those skilled in the art will understand thatthe teachings of the present invention have application to prostheticjoints for other applications and as such, the scope of the presentinvention will not be limited to elbow joints.

First bearing component 16′ is similar to first bearing component 16 inthat is includes a pair of condyle portions 60′ and a pin portion 62′.However, first bearing component 16′ is preferably unitarily formed withpin portion 62′ extending between the spherically-shaped bearingportions 66′ and fixedly coupling the spherically-shaped bearingportions 66′ thereto. Like first bearing component 16, each of thecondyle portions 60′ of first bearing component 16′ includes a slottedaperture 68 and a fastener aperture 72. Spherically shaped bearingportions 66′ collectively form a first bearing surface. Like firstbearing component 16, first bearing component 16′ may be made from anyappropriate bearing material, such as cobalt chromium alloy.

Second bearing component 18′ is similar to second bearing component 18in that it includes a cage portion 80′ which is fixedly coupled to theproximal portion 56 of second stem structure 14 and a bearing member 82′which is fixedly coupled to the cage portion 80′. For purposed ofclarity, bearing member 82′ has not been shown in cross section in FIG.5. Bearing member 82′ includes spherical bearing surfaces 84′ which areadapted to engage the spherically-shaped bearing portions 66′ of thecondyle portions 60′. The pair of bearing surfaces 84′ collectively forma second bearing surface that mates with the first bearing surface.Bearing member 82′ also includes a raised portion 160 which is adjacentthe spherical bearing surfaces 84′ and configured to clear pin portion62′, preferably without transmitting load therebetween (i.e. pin portion62′ preferably does not contact the surfaces of raised portion 160). Inthe particular embodiment illustrated, bearing member 82′ is fabricatedfrom polyethylene which has been molded to cage portion 80.Alternatively, bearing member 82′ may be fabricated from any otherappropriate material such as a cobalt chromium alloy, ceramics, orstainless steel.

To use unlinked prosthetic joint 10′, first stem structure 12 isimplanted in humerus 38′ such that proximal portion 34 is located in themedullary canal 36′ as shown in FIG. 5. Second stem structure 14 issimilarly implanted in ulna 54′ such that distal portion 50 is locatedin the medullary canal 52′. First bearing component 16′ is nextpositioned adjacent the distal portion 32 of first stem structure 12 andfurcations 42 are engaged to slotted apertures 68. Fasteners 64 areinserted through their respective mounting apertures 72 and threadablyengaged to their threaded fastener aperture 44. When fully seated, eachof the fasteners 64, extends through its respective furcation 42 toprevent its associated condyle portion 60′ from rotating relative tothereto. The proximal end of the ulna 54′ is positioned adjacent thedistal end of the humerus 38′ such that the pin portion 62′ is proximatethe raised portion 160 and the spherically-shaped bearing portions 66′of the condyle portions 60′ engage the spherical bearing surface 84′. Atthis point, first and second bearing components 16′ and 18′ are coupledtogether in an unconstrained or unlinked manner (i.e., held in positionby the soft tissues of the elbow). Construction of unlinked prostheticjoint 10′ in this manner provides many of the same advantages asmentioned above for linked prosthetic joint 10, such as the ability offirst and second bearing surfaces 16′ and 18′ to spread out the loadthat is transmitted through unlinked prosthetic joint 10′ over arelatively large area, rather than concentrate the load at a singlepoint or over a line of contact to thereby improve the durability ofunlinked prosthetic joint 10′.

As a surgeon may not always know prior to beginning an operation whethera patient would be better served by a linked or an unlinked jointprosthesis and as it is also occasionally necessary to convert andunlinked joint prosthesis to a constrained joint prosthesis, or viceversa, after implementation and use for a period of time, it is highlydesirable that the joint prosthesis be modular so as to provide thesurgeon with a high degree of flexibility which may be achieved in arelatively simple and cost-effective manner.

In FIGS. 6 and 7, a linked prosthetic joint constructed in accordancewith a second aspect of the present invention is generally indicated byreference numeral 10 b. Linked prosthetic joint 10 b is shown to includefirst stem structure 12, a third stem structure 180, first bearingcomponent 16, a third bearing component 182. Third stem structure 180 issimilar to second stem structure 14 in that it includes a distal portion184 which is adapted to fit within the medullary canal of an ulna. Theproximal portion 186 of third stem structure 180 is coupled to thirdbearing component 182.

Third bearing component 182 is similar to second bearing component 18 inthat it includes a cage portion 190 and a bearing member 192. Cageportion 190 is fixedly coupled to the proximal portion 186 of third stemstructure 180. Bearing member 192 is fixedly coupled to cage portion190. Bearing member 192 includes a pair of spherical bearing surfaces194 which are configured to engage the spherically-shaped bearingportions 66 of the condyle portions 60 and a through hole 196 which isconfigured to receive pin portion 52, preferably without transmittingload therebetween (i.e., pin portion 62 preferably does not contact thesurfaces of through hole 196). Bearing member 182 also includes alateral buttress 200. Lateral buttress 200 includes a supplementarybearing surface 201 which is configured for receiving a capitellum 202of the humerus 204. In the particular embodiment illustrated, thirdbearing component 182 is fixedly coupled to third stem structure 180 andas such, the combination of the second stem structure 14 and secondbearing component 18 is interchangeable with the combination of thethird stem structure 180 and the third bearing component 182. However,those skilled in the art will understand that second and third bearingcomponents 18 and 182 may also be releasably coupled to a stemstructure, thereby eliminating the need for a third stem structure 180which would otherwise be identical to second stem structure 14. Thoseskilled in the art will also understand that the lateral butress mayalternatively be coupled directly to the third stem structure 180, beingeither releasably attached thereto or integrally formed therewith.

In FIG. 8, another linked prosthetic joint constructed in accordancewith the teachings of a second aspect of the present invention isgenerally indicated by reference numeral 10 c. Linked prosthetic joint10 c is shown to include first stem structure 12, second stem structure14, a fourth stem structure 220, second bearing component 18, a fourthbearing component 222 and a fifth bearing component 224. Fourth stemstructure 220 includes a distal end 226 which is adapted to fit withinthe medullary canal of a radius and a proximal end 228 which is fixedlycoupled to fourth bearing component 222. Fourth bearing component 222includes a fourth bearing surface 230.

Fifth bearing component 224 is similar to first bearing component 16 inthat it includes, for example, a pair of condyle portions 60 and a pinportion 62 which permits first and fifth bearing components 16 and 224to be interchangeable. However, fifth bearing component 224 alsoincludes a lateral extension 240 which is adapted to replace at least aportion of the capitellum of the humerus. Lateral extension 240 definesa fifth bearing surface 242 which is configured to mate with fourthbearing surface 230. Preferably, at least a portion of each of thefourth and fifth bearing surfaces 230 and 242 is spherically shaped topermit loads transmitted therebetween to be spread out over a relativelylarge area, rather than be concentrated at a single point or along aline of contact.

In FIG. 9, a portion of a modular prosthetic joint kit constructed inaccordance with the teachings of a second aspect of the presentinvention is generally indicated by reference numeral 10 d. Modularprosthetic joint kit 10 d is shown to include second stem structure 14d, second bearing component 18 d, second bearing component 18 e and afastener 250.

Second bearing components 18 d and 18 e are similar to second bearingcomponents 18 and 18′, respectively, but are shown to be separable fromsecond stem structure 14. Second bearing components 18 d and 18 e alsoinclude a keel member 252, a clip member 254 and a fastener aperture 256which are formed in cage portions 80 d and 80 e, respectively. Keelmember 252 extends circumferentially around at least a portion of theperimeter of each of the cage portions 80 d and 80 e between clip member254 and fastener aperture 256. Clip member 254 includes a first portion258 which extends generally perpendicularly outward from its associatedcage portion and a second portion 260 which is coupled to the distal endof first portion 258. Second portion 260 extends generally outwardly andaway from first portion 258. Fastener aperture 256 is located acrossfrom clip member 254 and is sized to receive fastener 250.

Second stem structure 14 d is similar to second stem structure 14 inthat it includes a distal end 50 which is adapted to fit within themedullary canal of an ulna. Second stem structure 14 d also includes aproximal portion 56 d having a keel slot 264, a hook structure 266 andan internally treaded fastener aperture 268. Keel slot 264 is a slotthat is sized to receive keel member 252 in a slip fit manner. Keel slot264 and keel member 252 cooperate to resist relative medial-lateralmotion of cage portion (e.g. 80 d) relative to second stem structure 14.Hook member 266 is generally U-shaped and defines a clip aperture 270which is sized to receive clip member 254.

To use modular prosthetic joint kit 10 d, the distal end 50 of secondstem structure 14 d is inserted in the medullary canal of the ulna. Themodularity of the prosthetic joint kit 10 d permits the surgeon toassess the patient's elbow to determine if the patient would be betterserved by a linked or an unlinked joint prosthesis. Once a decision hasbeen made as to which type of joint prosthesis would better serve thepatient, the surgeon selects an appropriate one of the second bearingcomponents 18 d and 18 e, places its clip member 254 into the clipaperture 270, pivots the cage portion(i.e. 80 d) toward the proximal end56 d of the second stem structure 14 d to engage the keel member 252into the keel slot 264, inserts the fastener 250 through the fasteneraperture 256 and threadably engages the fastener 250 to the internallythreaded fastener aperture 268 to fixedly but releasably couple thesecond stem structure 14 d with the selected one of the second bearingcomponents 18 d and 18 e.

Those skilled in the art will understand that second bearing components18 d and 18 e may be couple to second stem structure 14 d in variousother manners as illustrated in FIGS. 10 through 15. In FIG. 10, secondbearing component 18 f is shown to include a generally L-shaped trayportion 280 which is fixedly coupled to cage portion 80 f. Tray portion280 includes a keel slot 282 and a fastener aperture 284. Keel slot 282is operable for receiving a keel member 286 formed into the proximal end56 f of second stem structure 14 f. Fastener aperture 284 is operablefor receiving a fastener 288 which may be threadably engaged to aninternally-threaded fastener aperture 290 in the proximal end 56 f ofsecond stem structure 14 f to thereby permit second bearing component 18f and second stem structure 14 f to be fixedly but releasably coupled.

When coupled together, keel slot 282 and keel member 286 cooperate toresist relative medial-lateral motion of cage portion 80 f relative tosecond stem structure 14 f. Additionally, tray portion 280 cooperateswith an L-shaped flange 292 to which it abuts to further resist relativerotation between second stem structure 14 f and cage portion 80 f.

In FIG. 11, second bearing components 18 g and 18 h are shown to includea stem member 300 which extends from their respective cage portions 80 gand 80 h. Stem member 300 is engagable with a stem aperture 302 formedinto the proximal end 56 g of second stem structure 14 g. As shown inFIG. 12, stem member 300′ may alternatively be incorporated into theproximal end 56 j of second stem structure 14 j and stem aperture 302′may be formed into cage portion 80 j of second bearing component 18 j.

To provide the surgeon with additional flexibility, second bearingcomponent 18 h is shown in FIG. 11 to be slightly longer than secondbearing component 18 g (i.e. the distances from the centerline ofbearing member 82 to the confronting surface 304 of their respectivecage portions 80 g and 80 h is shorter for second bearing component 18g). This variation between second bearing components 18 g and 18 hpermits the surgeon to adjust the length of prosthesis 10 g to take intoaccount the physical characteristics of the patient's arm.

Modularity may also be incorporated into first stem structure 12 k asshown in FIGS. 13 and 14. First stem structure 12 k is shown to includea stem member 320 and a yoke member 322. The proximal end 324 of stemmember 320 is adapted to fit within the medullary canal of a humerus andthe distal end 326 of stem member 320 terminates at a dovetail aperture328 having a pair of inwardly tapering walls 330 and a tapered retainingwedge 332. An internally threaded fastener aperture 334 extends throughretaining wedge 332. Yoke member 322 is shown to be similar to thedistal end 32 of first stem structure 12 as it includes furcations 42and threaded fastener apertures 44. Yoke member 322 also includes adovetail member 338 having a pair of outwardly tapering surfaces 340, awedge slot 342 and a through hole 344. Dovetail member 338 is configuredto mate with dovetail aperture 328 such that engagement of retainingwedge 332 to the upper surface 346 of wedge slot 342 forces taperedsurfaces 340 against a respective one of the inwardly tapering walls330. A fastener 350 is inserted through hole 344 and threadably engagedto internally threaded fastener aperture 334 to fixedly but releasablycouple yoke member 322 and stem member 320 together.

Referring back to FIG. 11, second bearing components 18 g and 18 h arealso shown to include a pair of tang members 360. Each of the tangmembers 360 extends outwardly from its respective cage portion (i.e., 80g) and in the particular embodiment illustrated, is generallyrectangularly shaped. Each of the tang members 360 is sized to engage atang recess 362 in the proximal end 56 g of the second stem structure 14g. Engagement of the tang members 360 into their respective tang recess362 inhibits relative rotation between the second stem structure 14 gand the second bearing components 18 g and 18 h.

In FIG. 15, second bearing component 18 m is shown to have a fasteneraperture 380 which is formed through a bearing member 82 m and cageportion 80 m. Second stem structure 14 m, which is a threaded fastener382 in this embodiment, is disposed through the fastener aperture 380 insecond bearing component 18 m and threadably engaged to the cancellousbone 384 of the ulna 54 m. Construction in this manner is advantageousin that it permits the extent of the trauma experienced by the patientto be minimized. To further this goal, the distal end 386 of cageportion 80 m is shown to be generally cylindrically shaped so as tominimize the amount of bone that must be removed to prepare the ulna 54m for the second bearing component 18 m.

In FIGS. 16 through 18, a portion of a modular prosthetic joint kitconstructed in accordance with the teachings of a third aspect of thepresent invention is generally indicated by reference numeral 10 n.Modular prosthetic joint kit 10 n is shown to include a bearing insert400, a retaining ring 402 and a second stem structure 14 n having anintegrally attached cage portion 80 n. Cage portion 80 n is shown toinclude a bearing aperture 406 for receiving bearing insert 400. In theparticular embodiment illustrated, cage portion 80 n also includes acircumferentially extending first ring groove 408 formed along theperimeter of bearing aperture 406 and operable for receiving a firstportion of retaining ring 402.

Bearing insert 400 is generally cylindrically shaped, having a pair ofspherical depressions 420 which collectively form a bearing surface thatis configured to mate with the spherically-shaped bearing portions 66 ofthe first bearing component 16. Bearing insert 400 also includes athrough hole 422 which is adapted to receive pin portion 52, preferablywithout transmitting load therebetween. A circumferentially extendingsecond ring groove 424 is formed in the outer perimeter of bearinginsert 400, the second ring groove 424 being operable for receiving asecond portion of retaining ring 402. Construction in this manner isadvantageous in that the surgeon may select a bearing insert 400 from aplurality of bearing inserts 400 to adapt prosthetic joint 10 n to thepatient.

In the particular embodiment illustrated, bearing aperture 406 is shownto include a plurality of radially outwardly extending tab apertures 430and bearing insert 400 is shown to include a plurality of radiallyoutwardly extending tabs 432. If desired, a first one of the tabapertures 430 and a first one of the tabs 432 may be sized differentlythan the remaining tab apertures 430 and tabs 432, respectively, to keythe bearing insert 400 to a specific orientation relative to second stemstructure 14 n.

With specific reference to FIG. 18, each of the pair of sphericaldepressions 420 includes a first spherical portion 450 and a secondspherical portion 454. Each of the first spherical portions 450 areformed into bearing insert 400 along an axis 456 that is coincident withthe longitudinal centerline of the bearing insert 400. Each of the firstspherical portions 450 are formed by a spherical radius approximatelyequal in magnitude to the spherical radius which defines thespherically-shaped bearing portion 66 of each of the condyle portions 60of first bearing component 16. The distance between the spherical radiialong axis 456 is equal to a predetermined distance, d.

The centerpoint 456 of the spherical radius that defines one of thefirst spherical portions 450 is employed to generate the secondspherical portion 454 on the opposite face of the bearing surface. Asecond centerline 468 is constructed from centerpoint 460 toward theopposite face at a predetermined constraint angel 470, such as 3.5degrees. The spherical radius that defines the second spherical portion454 on the opposite face is generated from a second centerpoint 472which is positioned along the second centerline 468 at a distance d fromcenterpoint 460. Construction of bearing insert 400 in this mannerpermits first bearing component 16 to rotate about centerline 456, aswell as to pivot relative to bearing insert 400 about thespherically-shaped bearing portion 66 of each of the condyle portions60.

A transition zone 480 is formed between each of the fist and secondspherical portions 450 and 454 wherein a radius is formed at theintersection of the radii which define the first and second sphericalportions 450 and 454 to “soften” the transition between the first andsecond spherical portions 450 and 454 to render the movement of thecondyle portions 60 over the first and second spherical portions 450 and454 more comfortable to the patient.

Those skilled in the art will understand that the degree of theconstraint may be defined by the constraint angle. Accordingly, modularprosthetic joint kit 10 n preferably includes a plurality of bearinginserts 400, each having a bearing surface with a second sphericalportion 454 that is defined by a different constraint angle. Thoseskilled in the art will also understand that the degree of theconstraint may be additionally or alternatively defined by a constraintcharacteristic, which is illustrated in FIGS. 19A through 19D.

In FIG. 19A, bearing insert 400 a has a first predetermined constraintcharacteristic orientation wherein the centerlines which define theradii which define first and second spherical portions 450 and 454 arecontained in a plane which is generally perpendicular to thelongitudinal axis of the ulna. Construction of bearing insert 400 a inthis manner provides a varying degree of axial constraint. In FIG. 19B,bearing insert 400 b has a second predetermined constraintcharacteristic wherein the centerlines which define the radii whichdefine first and second spherical portions 450 and 454 are contained ina plane which is at approximately 45° to the longitudinal axis of theulna. Construction of bearing insert 400 b in this manner provides avarying degree of a combination of axial and varus/valgus constraint. InFIG. 19C, bearing insert 400 c has a third predetermined constraintcharacteristic wherein the centerlines which define the radii whichdefine first and second spherical portions 450 and 454 are contained ina plane which is generally parallel the longitudinal axis of the ulna.Construction of bearing insert 400 c in this manner provides a varyingdegree of varus/valgus constraint. In FIG. 19D, bearing insert 400 d isconstructed in a manner that is generally similar to that of bearinginserts 400 a, 400 b and 400 c except that the constraint angle employedto construct bearing insert 400 d is rotated form point x1 to y1 asindicated in FIG. 19 d. As a result, there is no single line oforientation in which the constraint is limited. Construction of bearinginsert 400 d in this manner provides a varying degree of constraint inboth an axial direction and varus/valgus direction.

In FIGS. 20 through 22, a portion of a modular prosthetic joint kitconstructed in accordance with the teachings of an alternate embodimentof the third aspect of the present invention is generally indicated byreference numeral 10 p. Modular prosthetic joint kit 10 p is similar tomodular prosthetic joint kit 10 n in that it includes a bearing insert400 p and a second stem structure 14 p having a integrally attached cageportion 80 p.

Cage portion 80 p is shown to include a bearing aperture 406 p forreceiving bearing insert 400 p. In the particular embodimentillustrated, cage portion 80 p includes a plurality of tab apertures 430p, a plurality of tab slots 500 and a hook structure 502. Each of thetab apertures 430 p extends axially through cage portion 80 p andcircumferentially around a portion of bearing aperture 406 p. Each ofthe tab slots 500 intersects one of the tab apertures 430 p and extendscircumferentially around a portion of bearing aperture 406 p away fromits associated tab aperture 430 p. Hook structure 502 is adjacent one ofthe tab apertures 430 p and extends radially inwardly andcircumferentially around a portion of bearing aperture 406 p. A clipslot 510 is formed circumferentially through hook structure 502.

Bearing insert 400 p is generally similar to bearing insert 400 exceptfor the configuration of the plurality of tabs 432 p and theincorporation of a clip structure 520 into a bearing body 522. Each ofthe plurality of tabs 432 p is relatively thin and do not extend axiallyacross bearing insert 400 p. This permits the tabs 432 p of bearinginsert 400 p to be aligned to a tab aperture 430 p and bearing insert400 p to be rotated so that each of the tabs 432 p is disposed withinone of the tab slots 500 to thereby prevent bearing insert 400 p frommoving in an axial direction.

Clip structure 520 is preferably a metal or plastic fabrication which issuitable for molding into bearing body 522. Clip structure 520 includesan arm structure 530 which extends from a clip body 532 and terminatedat its distal end at a hook member 534. Clip structure 520 is configuredand incorporated into bearing body 522 such when bearing insert 400 p isrotated to engage tabs 432 p into tab slots 500, arm structure 530simultaneously engages clip slot 510 in hook structure 502. Rotation ofbearing insert 400 p to a predetermined rotational position relative tohook structure 502 permits hook member 534 to engage an edge 540 of hookstructure 502. Arm structure 530 resiliently biases hook member 534against edge 540, thereby inhibiting rotation of bearing insert 400 pwhich would cause tabs 432 p to disengage tab slots 500.

In FIG. 20B, bearing insert 400 p′ is illustrated to be configuredsimilarly to bearing insert 400 p except that a locking aperture 800 isformed into one of the tabs 432 p′. Bearing insert 400 p′ is insertedinto bearing aperture 406 p′ aligned such that each of the tabs 432 p′is aligned to an associated one of the tab apertures 430 p′. Bearinginsert 400 p′ is then rotated so that each of the tabs 500′ is disposedwithin one of the tab slots 440 p′ and locking aperture 800 is alignedto a corresponding locking aperture 802 formed in the integrallyattached cage portion 80 p′ of second stem structure 14 p′. Engagementof tabs 500 into their respective tab slots 440 p′ prevents bearinginsert 400 p′ from moving in an axial direction. Alignment of lockingapertures 800 and 802 to one another permits a pin 806 to be insertedtherethrough to prevent bearing insert 400 p′ from rotating relative tointegrally attached cage portion 80 p′. In the particular embodimentillustrated, pin 806 includes a head portion 808, a body portion 810 andan end portion 812. Head portion 808 has a diameter which is larger thanthe diameter of the hole formed by locking apertures 800 and 802. Bodyportion 810 is preferably smaller in diameter that the diameter of thehole formed by locking apertures 800 and 802.

A plurality of slots 814 fare formed in end portion 812 which creates aplurality of fingers 816 which are flexible relative to the longitudinalaxis of pin 806. Fingers 816 flex inwardly toward the longitudinal axisof pin 806 when pin 806 is inserted to locking apertures 800 and 802,eliminating the interference therebetween to permit the fingers 816 ofend portion 812 to pass through integrally attached cage portion 80 p′and bearing insert 400 p′. Once the fingers 816 have passed throughintegrally attached cage portion 80 p′ and bearing insert 400 p′, theyflex outwardly away from the longitudinal axis of pin 806 to inhibit theunintended withdrawal of pin 806 from locking apertures 800 and 802.Intended withdrawal of pin 806 from locking apertures 800 and 802 may beeffected through the flexing of fingers 816 inwardly toward thelongitudinal axis of pin 806.

Those skilled in the art will understand, however, that the pin 806 forlinking first and second stem structures 12 and 14 p′ may be constructeddifferently. As shown in FIG. 20C, for example, the pin 806′ includeshead and end portions 808′ and 812′ having chamfered abutting surfaces808 p′ and 812 p′, respectively. Additionally, the end portion 812′includes a chamfered lead portion 812 p″. Pin 806′ is installed bysimply pressing it through the bearing insert 400 p′.

In FIGS. 23 and 24, a portion of a modular prosthetic joint kitconstructed in accordance with the teachings of a fourth aspect of thepresent invention is generally indicated by reference numeral 10 q.Prosthetic joint kit 10 q is shown to include first stem structure 12,second stem structure 14, first bearing component 16 and second bearingcomponent 18 q. Second bearing component 18 q is substantially similarto second bearing component 18 except that cage portion 80 q is shown toinclude a cam structure 600. Cam structure 600 includes a lobe member602 that extends radially outwardly and terminates at a tip 604. Lobemember 602 is configured such that tip 604 contacts the base 102 ofU-shaped member 40 to inhibit further relative rotation between firstand second stem structures 12 and 14 when the first and second stemstructures 12 and 14 are placed in a position corresponding to themaximum extension of a patient's arm. Configuration of second bearingcomponent 18 q in this manner is advantageous in that it limits theamount by which a patient may rotate their ulna relative to theirhumerus to prevent hyperextension of the joint.

In FIGS. 25 and 26, a portion of a modular prosthetic joint kitconstructed in accordance with the teachings of a fifth aspect of thepresent invention is generally indicated by reference numeral 700.Prosthetic joint kit 700 is shown to include a first stem structure 702and a second stem structure 704. First stem structure 702 includes astem member 710, the distal end of which is configured to fit within themedullary canal of an ulna. A first bearing 712 and a coupling structure714 are incorporated into the proximal end of first stem structure 702.First bearing structure 712 is generally spherically shaped. Couplingstructure 714 includes a link member 720 and a retainer member 722. Linkmember 720 is fixed coupled to first bearing 712 at a first end and toretaining structure 722 at a second end with link member 720 extendingtherebetween along an axis generally coincident the longitudinal axis offirst stem structure 702. Retaining structure 722 is illustrated to bespherically shaped with flattened ends. According to various embodimentsa stop member 722′ is generally cylindrically shaped and the couplingmember 714 is coupled to the stop member 722′ along an axis that isgenerally perpendicular to a longitudinal axis of the stop member.

Second stem structure 704 is shown to include a stem member 730 with aproximal end that is configured to fit within the medullary canal of ahumerus. A second bearing structure 732 is incorporated into the distalend of second stem structure 704. Second bearing structure 732 includesa generally spherical second bearing surface 740 and a T-shaped couplingaperture 742. A first portion 744 of coupling aperture 742 has a widthwhich is larger than the width of retaining structure 722. First portion744 is oriented at a position of maximum flexion. In the particularembodiment illustrated, the position of maximum flexion is illustratedto be about 90° to the longitudinal axis of second stem structure 704.However, those skilled in the art will understand that the position ofmaximum flexion may be tailored in a desired manner and may range ashigh to an angle of approximately 135° to 150° to the longitudinal axisof second stem structure 704, depending on the particular application. Asecond portion 746 of coupling aperture 742 has a width which isslightly larger than that of link member 720. Second portion 746 extendscircumferentially around a portion of second bearing surface 740 in aplane that coincides with the longitudinal axis of second stem structure704. The first and second portions 744 and 746 of coupling aperture 742intersect and terminate at spherically shaped cavity 750.

To use prosthetic joint kit 700, first and second stem structures 702and 704 are inserted into the medullary canals of the ulna and humerus,respectively. First stem structure 702 is then positioned proximate thefirst portion 744 of coupling aperture 742 and retaining structure 722is inserted through first portion 744 and into spherically shaped cavity750. At this point, first and second bearing surfaces 712 and 740 are incontact with one another and transmit load therebetween rather throughcoupling structure 714. Coupling of first and second stem structures 702and 704 is complete when first stem structure 702 is rotated into secondportion 746. In this position, first and second stem structures 702 and704 are linked or constrained since the width of retaining portion 722is larger than the width of second portion 746 and thereby prevents thewithdrawal of first stem structure 702 from coupling aperture 742.

While the prosthetic joint devices 10 and 10 a have been illustrated ashaving modular flanges 20 that are fixedly but removably coupled to thefirst stem structure 12, those skilled in the art will understand thatthe invention, in its broader aspects, may be constructed somewhatdifferently. For example, the stem structure and modular flange may beunitarily formed as shown in FIG. 27. In this embodiment, the stem 12 pis illustrated to be similar to the stem 12, but includes a flangestructure 92 p having a flange member 96 p and a coupling portion 96 p′that couples the flange member 96 p to the distal portion 32 p of thestem 12 p. The flange member 96 p is generally parallel the stem member30 p and is employed to compress a bone graft against the stem member 30p. Unlike the modular flange 20 that was described in detail, above, theflange structure 92 p must be fitted over a gone graft 110 or the bonegraft must be placed into the aperture 800 between the stem member 30 p.

Another example of an integrally formed (i.e., non-removable) flangestructure is illustrated in FIGS. 28 and 29. In this example, the stem12 q is illustrated to be similar to the stem 12 p in that it includes aflange structure 92 q having a flange member 96 q and a coupling portion96 q′ that couples the flange member 96 q to the distal portion 32 q ofthe stem 12 q. The flange member 96 q, however, is arcuately shaped andincludes a contact tab 804. The flange structure 92 q is formed with apredetermined degree of resiliency, which may result from thecharacteristics of the material from which the flange structure 92 q isformed or by controlling the geometry (i.e., cross-sectional shaped andarea) of the flange structure 92 q. The resiliency of the flangestructure 92 q permits the flange member 96 q to act as a leaf springthat biases the contact tab 804 toward the stem member 30 q.Accordingly, the flange may be employed to apply compression to the bonegraft 110 q without fasteners or other securing means. As illustrated inFIG. 30, those skilled in the art will readily understand, however, thata predetermined amount of resiliency may also be incorporated into aflange structure 92 r that is fixedly but removably coupled to the stem12 r.

Those skilled in the art will also understand that although the modularflange 20 has been illustrated as being coupled to the stem 12 r via athreaded fastener 94 b, the invention, in its broader aspects, may beconstructed somewhat differently. For example, cables 810 are employedto fixedly but removably retain the flange structure 92 s to the stem 12s as illustrated in FIGS. 31 and 32. The stem 12 s is generally similarto the stem 12, but includes a first coupling feature 812 instead of thebore 100. The flange structure 92 s includes a flange member 96 s and acoupling portion 96 s′. The coupling portion 96 s′ includes a secondcoupling feature 814 that is configured to cooperate with the firstcoupling feature 812 to locate the flange member 96 s relative to thedistal portion 32 s of the stem 12 s. In the example illustrated, thefirst coupling feature 812 is a generally trapezoidal dovetail member816 that extends outwardly from the distal portion 32 s of the stem 12 sand the second coupling feature 814 is a dovetail aperture 818 that isformed into the coupling portion 96 s′ and sized to engage the dovetailmember 816 in with a line-to-line fit (i.e., with very little or noclearance). The dovetail member 816 is preferably integrally formed ontothe stem 12 s but may alternatively be an independently formed componentthat is fixedly coupled to the distal portion 32 s via an appropriatecoupling means, such as threaded fasteners, press-fitting or shrinkfitting.

The flange member 96 s is shown to include a plurality of cross-holes820 that extend completely through the flange member 96 s in a directionthat is generally perpendicular the longitudinal axis of the flangemember 96 s. The cross-holes 820 are sized to receive the cable 810. Asthose skilled in the art will understand, the cables 810 are firstssecured around the humerus 38 s and the ends of the cables 810 areloosely secured via an appropriate couple device, such as a cable sleeve822. The cables 810 are then tensioned to urge the flange member 96 sagainst the humerus 38 s and compress the bone graft 110 s by apredetermined amount. Thereafter, the coupling device is employed to fixthe ends of the cables relative to one another so as to maintain tensionin the cables 810.

While the first and second coupling features 812 and 814 have beenillustrated as being a dovetail member 816 and a dovetail aperture 818,respectively, those skilled in the art will appreciate that the firstand second coupling features 812 and 814 can be constructed somewhatdifferently. As illustrated in FIG. 33, for example, the first couplingfeature 812 t is illustrated as being a pair of pins 830 that arefixedly coupled to the distal portion 32 t of the stem 12 t and thesecond coupling feature 814 t is illustrated to be a corresponding pairof holes 832 that are formed into the coupling portion 96 t. The pins830 are preferably press-fit or shrunk fit into corresponding holes (notspecifically shown) that are formed into the distal portion 32 t of thestem 12 t but may be secured via other fastening means, such as welding,bonding, or threaded engagement where the pins 830 have a threadedportion that is threadably engaged to the holes in the distal portion 32t. Alternatively, the pins 830 may also be integrally formed as a partof the stem 12 t.

Another example is illustrated in FIGS. 34 and 35, where the firstcoupling feature 812 u is shown to include a mounting structure 840 withan arcuate mounting aperture 842 and the second coupling feature 814 uis shown to include an attachment hook 846. The mounting structure 840is coupled to the distal portion 32 u of the stem 12 u and extendsgenerally perpendicularly outwardly from the base 102 u of the U-shapedportion 40 u. The mounting aperture 842 is generally J-shaped andincludes a first portion 850, which is aligned generally perpendicularto the base 102 u, and an arcuate second portion 852, which extends awayfrom the stem member 34 u and the base 102 u. The attachment hook 846 isalso generally J-shaped, being configured to matingly engage themounting aperture 842. In this regard, the attachment hook 846 includesa leg portion 856 that extends downwardly from the flange member 96 uand an arcuate base member 858.

In coupling the first and second coupling features 812 u and 814 u,flange structure 92 u is initially positioned relative to the stem 12 usuch that the base member 858 is disposed within the first portion 850of the mounting aperture 842. The flange structure 92 u is then rotateddownwardly toward the stem member 34 u to permit the base member 858 toengage the second portion 852 of the mounting aperture 842. The cables810 are thereafter employed to fix the flange structure 92 u relative tothe stem 12 u.

While the invention has been described in the specification andillustrated in the drawings with reference to a preferred embodiment, itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention as defined in the claims. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment illustrated by the drawingsand described in the specification as the best mode presentlycontemplated for carrying out this invention, but that the inventionwill include any embodiments falling within the foregoing descriptionand the appended claims.

1. A prosthetic elbow kit comprising: a first stem structure having aproximal end and a distal end, the proximal end adapted to fit within amedullary canal of a humerus, the distal end terminating at a pair offurcations; a first bearing component having a pair of slotted aperturesand first and second condyle portions, each of the slotted aperturesslidingly engaging one of the pair of furcations, each of the first andsecond condyle portions having a first spherically-shaped bearingportion which collectively define a first bearing surface; and a secondstem structure having a proximal end and a distal end, the distal end ofthe second stem structure adapted to fit within an ulna; a secondbearing component coupled to the proximal end of the second stemstructure, the second bearing component including a pair of secondspherically-shaped bearing portions that collectively define a secondbearing surface configured to mate with the first bearing surface. 2.The prosthetic elbow kit of claim 1, wherein the first bearing componentfurther includes a pin portion, the pin portion intersecting each of thefirst spherically-shaped bearing portion and coupling the first andsecond condyle portions together.
 3. The prosthetic elbow kit of claim2, wherein the first bearing component is unitarily formed.
 4. Theprosthetic elbow kit of claim 2, wherein at least one of the first andsecond condyle portions includes a pin aperture sized to receive the pinportion.
 5. The prosthetic elbow kit of claim 2, wherein the secondbearing component includes a through hole sized to receive the pinportion.
 6. The prosthetic elbow kit of claim 2, wherein each of thefirst and second condyle portions is formed from a material selectedfrom a group of materials consisting of polyethylene, cobalt chromiumalloy, stainless steel, pyrolytic carbon and ceramics.
 7. The prostheticelbow kit of claim 1, further comprising a flange structure forreleasably engaging one of the first and second stem structures, theflange structure being configured to fixate a bone graft and compressthe bone graft against the one of the first and second stem structures.8. The prosthetic elbow kit of claim 7, wherein the flange structure isfixedly but releasably engaged to the one of the first and second stemstructures.
 9. The prosthetic elbow kit of claim 8, wherein a threadedfastener is employed to fixedly but releasably couple the flangestructure to the one of the first and second stem structures.
 10. Theprosthetic elbow kit of claim 7, wherein at least a portion of theflange structure is resiliently biased toward the one of the first andsecond stem structures.
 11. The prosthetic elbow kit of claim 1, furthercomprising a tissue fastener for engaging one of the first and secondstem structures, the tissue fastener being adapted to couple a softtissue to the one of the first and second stem structures.
 12. Theprosthetic elbow kit of claim 1, wherein the first and second stemstructures are hingedly coupled together when the first and secondbearing surfaces are mated together.
 13. The prosthetic elbow kit ofclaim 12, wherein the second bearing component is fixedly coupled to thesecond stem structure.
 14. The prosthetic elbow kit of claim 12, furthercomprising a third bearing component which is interchangeable with thesecond bearing component, the third bearing component having a lateralbuttress adapted for receiving a capitellum of the humerus.
 15. Theprosthetic elbow kit of claim 12, further comprising a third stem andthird and fourth bearing components, the third stem having a proximalend and a distal end, the distal end of the third stem adapted to fitwithin a medullary canal of a radius, the third bearing component coupleto the proximal end of the third stem and defining a third bearingsurface, the fourth bearing component being interchangable with thefirst bearing component, the fourth bearing component having a pair ofslotted apertures, first and second condyle portions and a lateralextension, each of the slotted apertures slidingly engaging one of thepair of furcations, each of the first and second condyle portions havinga first spherically-shaped bearing portion which collectively define afirst bearing surface, the lateral extension adapted to replace at leasta portion of a capitellum of the humerus, the lateral extension defininga fourth bearing surface configured to mate with the third bearingsurface.
 16. The prosthetic elbow kit of claim 15, wherein a least aportion of each of the third and fourth bearing surfaces is sphericallyshaped.
 17. The prosthetic elbow kit of claim 15, wherein the firstbearing surface supports the second bearing surface for pivotal movementthereon in an unlinked manner whereby the first and second stemstructures are not hingedly coupled.
 18. The prosthetic elbow kit ofclaim 1, wherein the second stem structure is a threaded fastener. 19.The elbow kit of claim 1, wherein one of the first and second stemstructures includes a cam structure with a tip, the tip being configuredto contact the other one of the first and second stem structures tolimit an amount by which the second stem structure can be rotatedrelative to the first stem structure.
 20. The elbow kit of claim 1,wherein each of the slotted apertures of the first and second condyleportions is a depression formed in a substantially planar exterior endwall of the first and second condyle portions, having an abutment walloperable to engage one of the pair of furcations as the furcation isslid into one of the slotted apertures, and a passage through a sidewallat the exterior end of the first and second condyle portions sized toallow sliding passage of the furcation into the depression; wherein thefirst spherically-shaped bearing portion is a curved end wall that iscurved and opposed to the substantially planar exterior end wall of eachof the first and second condyle portions.
 21. The elbow kit of claim 20,further compositing: a pair of bores, wherein each of the first andsecond condyle portions defines one of the pair of bores; and a pinoperable to be positioned in the pair of bores to couple the first andsecond condyle portions; wherein the pin is operable to extend through athrough bore defined by the second bearing component when coupling thefirst and second condyle portions; wherein the first spherically-shapedbearing portion is operable to engage the second bearing component andthe slotted apertures are operable to slidingly engage the pair offurcations when the first and second condyle portions are coupled withthe pin.
 22. A prosthetic elbow kit comprising: a first stem structurehaving a proximal end and a distal end, the proximal end adapted to fitwithin a medullary canal of a humerus, the distal end terminating at apair of furcations; a first bearing component having a pair of slottedapertures and first and second condyle portions, each of the slottedapertures slidingly engaging one of the pair of furcations, each of thefirst and second condyle portions having a first convexspherically-shaped bearing portion that has an apex on a first axis thatis substantially perpendicular to a second axis of each slottedaperture, wherein collectively the first convex spherically-shapedbearing portion of both the first and second condyle portions define afirst bearing surface; and a second stem structure having a proximal endand a distal end, the distal end of the second stem structure adapted tofit within an ulna; and a second bearing component coupled to theproximal end of the second stem structure, the second bearing componentincluding a pair of concave spherically-shaped bearing portions thatcollectively define a second bearing surface configured to mate with thefirst bearing surface; wherein each slotted aperture is defined by afirst passage in an exterior sidewall and a second passage in anexterior end wall of the first and second condyle portions; wherein onefurcation is operable to slide into the slotted aperture through thefirst passage.
 23. The prosthetic elbow kit of claim 22, wherein thefirst bearing component further includes a pin portion, the pin portionintersecting each of the first convex spherically-shaped bearingportions to couple the first and second condyle portions together. 24.The prosthetic elbow kit of claim 22, wherein the pin is positionedbetween the first and second condyle portions along the first axis. 25.The prosthetic elbow kit of claim 24, wherein the second bearingcomponent defines a bore sized to allow the pin to pass through thebore; wherein the first and second condyle portions are operable to beconnected with the pin extending through the bore in the second bearingcomponent and the slotted apertures of the first and second condyleportions are operable to allow the pair of furcations to slide intoengagement with the first and second condyle portions.
 26. Theprosthetic elbow kit of claim 25, wherein each of the pair of secondconcave spherically-shaped bearing portions include a first concavebearing surface defined around a first center axis and a second concavebearing surface defined around a second center axis at an angle to thefirst center axis; wherein each of the pair of second concavespherically-shaped bearing portions is configured to engage one of theconvex spherically-shaped bearing portion of the first or second condyleportions.
 27. A prosthetic elbow kit comprising: a first stem structurehaving a proximal end and a distal end, the proximal end adapted to fitwithin a medullary canal of a humerus, the distal end terminating at apair of furcations; a first bearing component, including, a firstcondyle portion extending along a first axis having a first sidedefining a first slotted aperture, wherein the first slotted aperture isa depression in an end wall of the first condyle portion that defines asecond axis non-parallel to the first axis and a second side extendingalong the first axis away from the first side defining a first convexspherically-shaped bearing portion being convex along the first axisaway from the first side, and a second condyle portion extending along athird axis having a third side defining a second slotted aperture,wherein the second slotted aperture is a depression in an end wall ofthe second condyle portion that defines a fourth axis and a fourth sideextending along the third axis away from the third side defining asecond convex spherically-shaped bearing portion being convex along thethird axis away from the third side, wherein the first convexspherically-shaped bearing portion and the second convexspherically-shaped bearing portion collectively define a first bearingsurface; a second stem structure having a proximal end and a distal end,the distal end of the second stem structure adapted to fit within anulna; and a second bearing component coupled to the proximal end of thesecond stem structure, the second bearing component including, a pair ofopposed concave spherically-shaped bearing portions that collectivelydefine a second bearing surface configured to mate with the firstbearing surface.
 28. The prosthetic elbow kit of claim 27, wherein eachof the pair of opposed concave spherically-shaped bearing portions havea base defining a plane; wherein each of the pair of opposed concavespherically-shaped bearing portions defines an apex point furthest fromthe plane; wherein the apex point of each of the pair of opposed concavespherically-shaped bearing portions is the point nearest the other ofthe pair of opposed concave spherically-shaped bearing portions.
 29. Theprosthetic elbow kit of claim 27, wherein each of the pair of opposedsecond concave spherically-shaped bearing portions include a firstconcave bearing surface defined around a first center axis and a secondconcave bearing surface defined around a second center axis at an anglerelative to the first center axis; wherein each of the pair of secondconcave spherically-shaped bearing portions is configured to engage oneof the first or second convex spherically-shaped bearing portionsdefined by the first or second condyle portions.
 30. The prostheticelbow kit of claim 27, further comprising a lateral buttress; whereinthe lateral buttress extends laterally from either of the first bearingcomponent or the second bearing component; wherein the lateral buttressis operable to receive the capitellum or replace the capitellum.
 31. Theprosthetic elbow kit of claim 27, further comprising: a cam structurewith a tip defined by the second stem structure extending proximallyfrom the second stem structure; wherein the first stem structure definesa cross-bar between the pair of furcations; wherein the tip is operableto contact the cross-bar to limit an amount which the second stemstructure can be rotated relative to the first stem structure.